Lai, 49, has reportedly confessed under questioning to accepting NT$1 million from a bidder for the Taipei Twin Towers project.

"Ma loves to flaunt his corruption-free image, but today his favorite is embroiled in a serious scandal," said Democratic Progressive Party (DPP) Caucus Secretary-General Chiu Yi-ying (邱議瑩) at the Legislative Yuan yesterday.

Lai is joining ex-Cabinet Secretary-General Lin Yih-shih (林益世) and ex-Nantou Magistrate Lee Chao-ching (李朝卿), in a line of a senior KMT officials who have been implicated in bribery cases over the past year.

The president has attempted to distance himself from Lin and Lee, but he won't be able to do the same with Lai, who is "100 percent Ma's protege," said Chiu.

The KMT councilwoman served a stint as former KMT spokeswoman before rising to the directorship of Ma's party office. Lai is also a long-standing political consultant for Ma, as well as for Lin Yi-shih and his wife, Vice President Wu Den-yih (吳敦義) and Taiwan's U.S. representative King Pu-tsung (金溥聰), according to the DPP caucus.

"Ma has groomed Lai from the start and even appointed her to direct his own office. Today, he must provide an explanation," said DPP Legislator Chen Ting-fei (陳亭妃).

"If Ma and Lin (Yih-shih) are close, then Ma and Lai are the closest of the close of the close."

According to prosecutors, other suspects in the Twin Towers case include Taipei City Finance Department Commissioner Chiu Da-chan (邱大展) and ex-Director Jia Er-ching (賈二慶) of the of the Department of Rapid Transit Systems and Michael Ho (何岳儒), chairman of the bidding developer.

The DPP caucus said the Lai probe is set to uncover "plenty of high-level KMT officials behind the scenes" including Taipei City Mayor Hau Lung-bin (郝龍斌).